Antisense technology is an effective means for reducing the expression of one or more specific gene products and can therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications. Chemically modified nucleosides are routinely used for incorporation into antisense sequences to enhance one or more properties such as for example nuclease resistance. One such group of chemical modifications includes bicyclcic nucleosides wherein the furanose portion of the nucleoside includes a bridge connecting two atoms on the furanose ring thereby forming a bicyclic ring system. Such bicyclic nucleosides have various names including BNA's and LNA's for bicyclic nucleic acids or locked nucleic acids respectively.
Various BNA's have been prepared and reported in the patent literature as well as in scientific literature, see for example: Singh et al., Chem. Commun., 1998, 4, 455-456; Koshkin et al., Tetrahedron, 1998, 54, 3607-3630; Wahlestedt et al., Proc. Natl. Acad. Sci. U.S.A., 2000, 97, 5633-5638; Kumar et al., Bioorg. Med. Chem. Lett., 1998, 8, 2219-2222; Wengel et al., PCT International Application number PCT/DK98/00303 (published as WO 99/14226 on Mar. 25, 1999), filed Sep. 14, 1998; Singh et al., J. Org. Chem., 1998, 63, 10035-10039, the text of each is incorporated by reference herein, in their entirety. Examples of issued U.S. patents and published applications include for example: U.S. Pat. Nos. 6,770,748, 6,268,490 and 6,794,499 and published U.S. applications 20040219565, 20040014959, 20030207841, 20040192918, 20030224377, 20040143114, 20030087230 and 20030082807, the text of each is incorporated by reference herein, in their entirety.
Various 5′-modified nucleosides have been prepared and reported in the patent literature as well as in scientific literature, see for example: Mikhailov et al., Nucleosides and Nucleotides, 1991, 10, 393-343; Saha et al., J. Org. Chem., 1995, 60, 788-789; Beigleman et al., Nucleosides and Nucleotides, 1995, 14, 901-905; Wang, et al., Bioorganic & Medicinal Chemistry Letters, 1999, 9, 885-890; and PCT Internation Application WO94/22890 published Oct. 13, 1994, the text of each is incorporated by reference herein, in their entirety.
Consequently, there remains a long-felt need for agents that specifically regulate gene expression via antisense mechanisms. Disclosed herein are 5′-modified BNA's and antisense compounds prepared therefrom useful for modulating gene expression pathways, including those relying on mechanisms of action such as RNaseH, RNAi and dsRNA enzymes, as well as other antisense mechanisms based on target degradation or target occupancy. One having skill in the art, once armed with this disclosure will be able, without undue experimentation, to identify, prepare and exploit antisense compounds for these uses.